This proposal responds to Request for Applications RFA-MH-08-131, which seeks Collaborative R01 applications that propose to enrich pre-existing resources for schizophrenia in the NIMH Human Genetics Initiative and to apply genomic methods to further our understanding of the molecular etiology of the disorder. The overarching aims of this proposal are to quickly and cost-effectively ascertain a large sample of trio families affected by schizophrenia, and to discover causal variants for the disorder in the first family-based genome-wide association study (GWAS) of the illness. In our recently completed NIMH-funded Genetic Linkage Study of Schizophrenia (R01MH059624; PI: Ming T. Tsuang), we established a large and efficient ascertainment network and infrastructure in Taiwan, which will again be utilized and expanded in the proposed study. Through additional ascertainment within this framework, we will collect an aggregate sample of 5,000 trios with adequate power for detecting in a GWAS those variants that make even small contributions to the risk for the disorder. We will meet the overarching goals of this project by accomplishing several Specific Aims, as follows: 1) Supplement our previously collected sample of 1,200 Han Chinese schizophrenia-affected nuclear families from Taiwan by rapidly screening and collecting an additional 3,800 trios from ten ascertainment sites in Taiwan; 2) Assess the association of schizophrenia with a genome-wide panel of single-nucleotide polymorphisms and their constituent haplotypes; 3) Perform a genome-wide survey for copy-number variations related to schizophrenia; 4) Test for gene-gene interactions (epistasis); 5) Test for gene-environment interactions, such as the well-established effect of season of birth; 6) Analyze quantitative schizophrenia phenotypes, such as symptom scores and age at onset; and 7) Enhance the NIMH Genetics Initiative collections by sending all clinical data, biomaterials, and genotypes to the appropriate repositories. The project would achieve the goals of the RFA by enriching the existing resources of the NIMH Human Genetics Initiative and by applying the latest genomic research methods to further our understanding of the molecular etiology of the disorder. Also, by capitalizing on an existing clinical infrastructure and an efficient screening and assessment protocol, we will obtain a well-powered sample in a very rapid and cost-effective manner.